Subject: Returned mail: see transcript for details

From: Mail Delivery Subsystem <[email-masked]>
Date: Thu, 9 Aug 2007 12:21:50 -0400 (EDT)

The original message was received at Thu, 9 Aug 2007 12:21:39 -0400 (EDT)
from exprod6mx197.postini.com [64.18.1.101]

   ----- The following addresses had permanent fatal errors -----
<[email-masked]>
    (reason: 550 5.1.1 <[email-masked]>... User unknown)

   ----- Transcript of session follows -----
... while talking to [10.4.40.100]:
>>> DATA
<<< 550 5.1.1 <[email-masked]>... User unknown
550 5.1.1 <[email-masked]>... User unknown
<<< 503 5.0.0 Need RCPT (recipient)